All-in-One Chalk Plotter for Lines, Angles, Circles and Ellipses

The problem

Drawing precise geometric shapes on a classroom board or large drafting surface normally requires several separate instruments. A teacher reaches for a long ruler to draw a line, picks up a protractor to mark an angle, and then switches to a large compass to sweep a circle or arc. Each time a tool is swapped, the reference point can shift, reducing accuracy. Carrying and storing a full set of oversized board tools takes space, and holding them steady against a vertical surface demands extra effort, especially when tracing complex curves like ellipses.

The solution

This integrated plotter solves the problem by combining the drawing functions into a single mechanical linkage anchored to the work surface.

1. Two bases (1) sit on the board, each fitted with a suction cup (17) on its bottom to hold the unit in place.
2. A first polished rod shaft (2) connects the two bases. A slider (3) moves along this shaft.
3. One end of a second polished rod shaft (4) hinges to the first shaft through the slider, allowing the second shaft to pivot and slide.
4. A sliding groove (5) on the second shaft accepts a sliding block (8), which hinges to an M rod (6) positioned below the groove.
5. An N rod (7) runs on a parallel surface beneath the M rod, joined to it by a shaft sleeve (9).
6. A chalk support frame (10) is mounted at one end of the N rod, holding the drawing medium against the surface.
7. Two connecting rods (11) are movably joined together; one end mates with the sliding groove and the other with a horizontal protruding end of the shaft sleeve, coordinating the movement for ellipse generation.

Who it is for

• Educational equipment suppliers sourcing geometry tools for primary and secondary schools that want to reduce the number of separate board instruments teachers carry.
• Art and design studios needing a mechanical aid for drawing large-scale ellipses and arcs directly on walls or boards during layout work.
• Office and training room outfitters equipping conference spaces where presenters sketch diagrams on whiteboards or chalkboards frequently.
• Toy and game manufacturers developing home or club teaching kits for geometry and board-game design exercises.

How it works

The main parts

Operating steps

1. Mount the bases. Press the suction cups against the board so the first polished rod shaft is fixed horizontally.
2. Set the shape. Loosen the relevant adjustment knobs. To draw a line, align the rods straight. For an angle, pivot the second shaft using the angle plate scale. For a circle, fix the slider and swing the N rod around it. For an ellipse, engage the two connecting rods between the sliding groove and the shaft sleeve.
3. Lock the dimensions. Tighten the six adjustment knobs (201 through 206) to secure the slider, the hinges, the sliding groove and the rods at the chosen positions.
4. Insert the chalk. Place a piece of chalk into the chalk support frame, where the spring pushes the sleeve downward.
5. Draw. Move the linkage smoothly across the board. The rolling steel ball under the N rod helps it glide over the surface.

Applications

Classroom geometry lessons

Mathematics teachers use the plotter to demonstrate how lines, angles and circles relate to one another without putting down one tool to pick up another. The suction cups keep the base steady on a vertical chalkboard, letting the instructor focus on the explanation rather than holding the instrument in place.

Architectural and interior layout sketches

Designers marking large arcs or elliptical arches on a wall or floor plan board can set the connecting rods to the required proportions. The integrated linkage maintains the ratio throughout the stroke, producing a consistent curve faster than plotting individual points by hand.

Art studio composition

Artists preparing murals or large canvases often need precise geometric under-drawings. The spring-loaded chalk frame applies even pressure, preventing skipped lines on textured surfaces, while the angle plates help establish perspective grids directly on the working surface.

Teacher training workshops

Instructors learning board-work techniques benefit from a single device that demonstrates multiple drafting principles. Trainers can show how adjusting the slider position changes a circle into an ellipse, making the geometric relationship visible in one continuous motion.

Home education and board games

Parents teaching geometry at home or running educational board-game clubs can use the plotter as a hands-on aid. Its compact linkage folds together for storage, and the marked scales on the rods and chutes allow children to read measurements as they draw.

Where it is less suitable

• Paper drafting desks - the suction cups and overall size are intended for boards or large smooth surfaces, not standard desk pads.
• Permanent ink or paint applications - the chalk support frame is designed for dry chalk; liquid markers or paint brushes would require a different holder.
• CNC or digital plotting - this is a manual mechanical linkage for visual demonstration, not a motorized or computer-controlled machine.